Starting from discussion at T169828#3415358 referencing issues with Charter in Polish and Turkish language characters, we need to clarify our serif font family choice more explicitly for developers (and probably de-emphasize Charter and stronger emphasize Charis) in average Wikimedia projects.
Charter appears to have extremely poor support for non-English text. I installed it locally from the site you linked and tried with the Polish test sentence "Zażółć gęślą jaźń." – out of the 9 accented characters in Polish, only 2 are supported ("ó" and "ł"). I think this is entirely hopeless.
Polish characters in Charter Charis